The invention relates to a transfer device for a linear conveyor, and more particularly for a conveyor for conveying mail bins used in a postal sorting machine.
French Patent Document No. 2 772 734 discloses a transfer device for a linear conveyor for conveying various parcels, that conveyor having swinging angled levers suitable for selectively exerting a thrust force on the parcels placed on the conveyor so as to move them to a fixed framework, the direction of thrust being substantially perpendicular to the parcel conveying direction. That framework is disposed between the linear parcel conveyor and another conveyer of any type serving to remove the parcels as they arrive at that location. A parcel already present on the framework is removed from the framework to the removal conveyor by thrust from another parcel placed on the conveyor, the other parcel itself being pushed towards the framework by a swinging angled lever of the transfer device.
A swinging lever is not suitable for transferring mail bins because the bearing force that it can exert on an empty mail bin resting on the linear conveyor is a point force that might deform the bin, especially when the empty bin reacts by pushing a bin that is present on the framework and that is filled with mail items. In addition, since the area of contact between the swinging lever and the mail bin is small, a vertical reaction can occur between the full bin as pushed by the empty bin and the empty bin pushing it if the faces of the bins are not parallel (for example, if they are tilted) or if they have ribs. When a linear conveyor as known from that document is used in a postal sorting machine, the location of the framework corresponds to a sorting outlet at which the mail items are tipped into a mail bin. Under the sorting outlets, it can be necessary to place bins in a tilted position rather than flat, so as to avoid losing mail items, and so as to obtain more orderly stacking of the mail items in the bins. Unfortunately, the configuration of the transfer device known from that document does not make it possible to bring an empty bin to a tilted position on the framework.
An object of the invention is, more particularly, to remedy those drawbacks by providing a transfer device suitable for extracting an empty bin from a linear conveyor and for moving it flat to a loading location corresponding to a sorting outlet where it is placed so that it is tilted at the same time as a tilted full bin resting at this location is being extracted and moved flat to a removal conveyor.
To this end, the invention provides a transfer device for a linear conveyor, the transfer device comprising a fixed framework placed on one side of the linear conveyor and means for moving objects towards the framework in a transfer direction that is different from the conveying direction of said conveyor, said transfer device being characterized in that said means comprise an object transporter structure mounted in said framework to move in a substantially vertical direction in order to occupy a transfer position in which the transporter structure is disposed above the linear conveyor or a retracted position in which the transporter structure is disposed below the linear conveyor, and in that said transporter structure extends across the linear conveyor and extends in the transfer direction on one side of the conveyor. With such a transfer device, an empty mail bin resting on the linear conveyor is raised by the transporter structure above the linear conveyor to be moved in a transfer direction, while a full mail bin resting on the transporter structure at the framework is being removed without being pushed by the empty bin. As a result, neither the empty bin nor the full bin undergo deformation while they are being transferred.
To make it possible for an object extracted from the linear conveyor to be put in a tilted position on the framework after it has been transferred from the linear conveyor, provision is made in the transfer device of the invention for the framework to form two horizontal margins which are substantially parallel to the transfer direction on the side of the conveyor, and between which the transporter structure can be raised and lowered. The transporter structure is disposed below the two margins when it occupies its retracted position, and above the two margins when it occupies its transfer position, and the two margins are offset in the vertical direction. In this way an object placed on the transporter structure can rest on the two margins so that it is tilted when the transporter structure is in its retracted position.
To make it possible for a tilted object to be positioned accurately on the framework, the framework is provided with an abutment disposed at one end of a margin. In addition, a pivotally-mounted lever is provided to exert a thrust force on the transporter structure towards said abutment when the transporter structure is moved from its transfer position to its retracted position.
The transfer device of the invention is particularly suitable for a linear conveyor having two motor-driven parallel belts. In which case, the transporter structure may be provided with one or more motor-driven belts serving to transfer objects in said transfer direction. The one or more motor-driven belts of the transporter structure are guided in the transporter structure to form a substantially horizontal transport surface in two portions, one of the two portions extending between the two belts of the linear conveyor, and the other portion extending on said side of the linear conveyor.
A plurality of transfer devices of the invention may be disposed in succession along a linear conveyor by extending across said conveyor at right angles or at some other angle. Similarly, a plurality of linear conveyors, each of which is equipped with a plurality of transfer devices may be superposed to handle mail bins automatically in a postal sorting machine having a plurality of sorting levels.